Thought I had found a nifty trick for using bitmap images as symbols but not quite there. I made a screen shot of a specific coach light fixture a client wants on the front of their house design. I used Photoshop Elements to make the surrounding background of the image into a transparent background. I was able to make a symbol of the light fixture image. But, when I then inserted into in a drawing, the background rectangle of the image was a medium gray color and showed up on the drawing. I then tried changing the image background to white but that symbol also inserted in the DCAD drawing with the gray, noticeable, background.

I did a crop of the fixture to the shape of the fixture but even making that a symbol, it shows up with a surrounding rectangle when its inserted as a symbol. I know DCAD is just inserting a rectangle of a bitmap and doesn't "see" just the image. If there was a way for bitmaps to be inserted with transparent backgrounds that wouldn't print, we would have a real coup for making future drawing symbols.

I found the "fix" for this technique. The image can be made into a symbol but the background of the image will remain a rectangle. Insert the symbol into the drawing. Make a self xRef of the symbol (image). Use the polygon menu setting for xRef clip cubes and outline the image to crop out the background. I found it necessary to outline the image part with a polyline so that when making the self xRef, I could see where to click.

This method crops out the background so only the desired bitmap image is noticeable on the screen and when printed. This xRef can be copied all over the drawing and it retains the xRef clipped properties.

We use a similar technique for importing things like aerial photos, etc. The self-xref is much easier to rotate, scale, etc. and requires little or no processing of the bitmap itself. Use a polyline to define the area to be masked and then use it to define the final XClip "by Entity"

I usually just insert the image, edit the perimeter of the image directly leaving the 4 corners in place as to not affect the aspect ratio of the image. (Like in this video). Then copy the clipped image to the clipboard and paste it back into the drawing as a new Symbol using Ctrl+SHIFT+V.

Also now that Symbols can be directly S-Clipped it gives you a few more options if needed for clipping the symbol in a different way if needed like using xclips. I would guess this method is less overhead than a self xref, but your mileage may very.

Dcad does not recognize "transparency" found in pngs, but there is a work around...

Take a look at the fencing and lattice material that comes with Dcad - the images use 100% black where "transparent" would normally be indicated. In the Edit Materials dialog, under the texture bitmap field there is the option to "Render black as transparent", selecting that causes 'black' to act as 'transparent'. Of course, anything in the image that is black that you want to keep needs to be made 'almost black' (RGB=1,1,1), but maybe this trick will help you achieve the result you are looking for.